1. Field of the Invention
The present invention relates to a pre-loader sensor unit for activating the functional operation of a pre-loader which is applicable to a webbing retractor of a seat belt device, which enables the device to tightly constrain a vehicle passenger with a webbing when the vehicle speed quickly decelerates, and furthermore, the invention also relates to mechanism for securing the webbing retractor to the vehicle body.
2. Description of Related Art
A conventional seat belt installed in a vehicle body constrains the driver and passengers by means of a webbing when the vehicle speed quickly decelerates. However, if there is a large interval between the webbing and the driver, the constraining effect cannot be fully exerted. To compensate for this, a webbing retractor has been devised which is integrated with a preloader for tightly constraining the driver with a webbing by forcibly pulling the webbing in the retracting direction when the vehicle speed quickly decelerates. The preloader is provided with a preloader sensor. When the vehicle speed quickly decelerates, the preloader sensor operates and activates the preloader. The preloader sensor is provided with a safety device which enables the alternation of the preloader sensor to one or the other of an operation-capable and a non-operational state, by a manual adjustment.
It is essential that the functional operation of the preloader sensor be correctly activated, that is, activated only when the vehicle speed quickly decelerates. Concretely, it is essential for the functional operation of the preloader sensor to be reliably blocked until after the webbing retractor has been completely installed in the vehicle body, and alos, to be blocked if and when the webbing retractor is removed from the vehicle body. It is also essential for the functional operation of the preloader sensor to be blocked when the webbing retractor is being transported before it is installed in the vehicle body or after it is removed from the vehicle body.
In a conventional webbing retractor provided with a conventional preloader sensor, such safety devices are typically separate from and independent of the mechanical parts for installing the webbing retractor in the vehicle body. Because of this, the process of installing the webbing retractor in the vehicle body by means of fixing parts must be executed independently of the process of effecting the operational (operation-capable) state of the preloader sensor through the adjustment of a safety device.
Further, such fixing parts have the function of securing the webbing retractor to the vehicle body, whereas the safety device merely has the functions of blocking and activating the operational state of the preloader. As a result, it is likely that vibration which occurs in the course of installing or removing the webbing retractor in and from the vehicle body will be transmitted to the operational center of the preloader sensor, thus causing the preloader sensor to malfunction. The same applies to the case of transporting the webbing retractor as well.